Today's mobile networks/communication systems have a strong potential for energy savings. The design of communication systems has until now been focused optimizing coverage and capacity for high traffic load scenarios and little attention has been put on network energy savings for the more common low traffic scenarios. This design philosophy has resulted in that today's radio base stations consume more than 50% of the maximum energy consumption even when no traffic is served. However, there is no fundamental reason why an idle base station needs to consume more than e.g. 1% of the maximum energy consumption when it is idle.
Not all cellular sites comprised in a communication system are connected to the Alternate Current (AC) grid and in a typical network different sites may use different energy supply sources such as e.g. AC grid, diesel, solar, wind, hybrid etc, see FIG. 1. These energy sources differ significantly in both marginal energy cost, i.e. the additional cost of producing one extra kWh; and in marginal carbon dioxide emissions i.e. the additional carbon dioxide emissions of one extra kWh produced. The energy solutions also differ in energy storage possibilities. Diesel can be saved for later use but wind and solar energy are intermittent and once the back-up battery of an off-grid site is fully charged, any additional renewable energy supply will be wasted. Thus an off-grid site with renewable energy supply may have an energy surplus that is wasted, e.g. during weekends with low traffic or on a windy or sunny day.
By simply minimizing the network energy consumption at all times operators do not automatically also minimize energy cost and/or carbon dioxide emissions.
Further, in a communication system according to known solutions the requirements on functionality and operability, comprising high reliability, availability and low power consumption, is a problem to achieve. Known communication systems and their power supplies are for the most time built-up by units from different types and manufactures, which usually implies that each power supply unit must function without knowing or being able to communicate with other power supply units comprised within the communication system. This renders difficulties when trying to optimize the functionality and efficiency of the communication system in total.